RE: [wsbpel] Issue 147 - Proposal For Vote

["Eckenfels. Bernd" <B.Eckenfels@seeburger.de>]

Hello Yaron,

I am pretty suprised that you changed your proposal that quickly. :) If
somebody still thinks about your fist object-oriented-alias iterator, I
would be happy to brain storm it on that a bit more. Besides the
complexity of input-output/snapshot/concurrent/slot-reservations id had
some charme.

Otherwise if everybody agrees that the simple counter solution is the
way to go I think your proposal for that way is great, covering all the
aspects needed.

(To make it a bit more simple I would remove the count-direction and
enforce counting from start to end in +/-1 steps automatically -or- keep
the definded direction as step=int?)

Greetings
Bernd

-----Original Message-----
From: Yaron Y. Goland [mailto:ygoland@bea.com] 
Sent: Monday, April 18, 2005 8:00 PM
To: wsbpeltc
Subject: [wsbpel] Issue 147 - Proposal For Vote

147 - Serial and Parallel Foreach

Proposal: Introduce a foreach to BPEL with both serial and parallel
semantics.

Rationale: Just check the issue list for issue 147. There is a whole
series of mails attesting to how important this activity is.

Introduce a section 12.6

12.6 - foreach

<forEach counterName="ncname" parallel="yes|no" count="up|down"? 
standard-attributes>
     standard-elements
     <startCounterValue expressionLanguage="anyURI">
        ...
     </startCounterValue>
     <finalCounterValue expressionLanguage="anyURI">
        ...
     </finalCounterValue>
     Scope
</foreach>

The foreach activity is an iterator that will repeat its contained scope
activity exactly N+1 times where N equals the absolute value of the
value returned by the expression in <startCounterValue> subtracted from
the value returned by the expression in <finalCounterValue>.

When the foreach activity is started the expressions in
<startCounterValue> and <finalCounterValue> are evaluated. Both
expressions MUST each return a value of type xs:int or the
bpws:forEachCounterError fault MUST be thrown. If the expression
language used in either element happens to be
urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0 then the expressions
contained in the two elements MUST be wrapped in implicit calls to the
round(number()) functions.

The count attribute is optional and defaults to "up". If count equals
"up" and the startCounterValue is greater than the finalCounterValue or
if count equals "down" and the startCounterValue is less than the
finalCounterValue then a bpws:forEachCounterError fault MUST be thrown. 
It is always legal to have the startCounterValue equal the
endCounterValue regardless of the value of the count attribute.

The Scope activity MUST NOT have a variable explicitly declared in it
with the same name as contained in the counterName attribute, a
violation of this requirement MUST be detected statically.

If parallel="no" then this is a serial foreach where the enclosed scope
activity will be repeated N+1 times. During each repetition a variable
of type xs:int will be created on the enclosed scope activity with the
name specified in the counterName attribute. The counter variable's
creation and initialization MUST occur before any other variables on the
enclosed scope activity are declared, therefore other variables declared
on the enclosed scope activity MAY refer to the counter variable in
their own initializations. The counter variable is local to the enclosed
scope and although its value can be changed during an iteration that
value will be lost when the enclosed scope exits and will not affect the
value that the next iteration's counter will be set to.

The first iteration of the scope will see the counter variable set to
the startCounterValue. The next iteration will cause the counter
variable to be set to the startCounterValue plus one if the count
attribute equals "up" or by minus one if the count attribute equals
"down". Each subsequent iteration will increment/decrement the
previously initialized counter value until the final iteration where the
counter will be set to the finalCounterValue.

If parallel="yes" then this is a parallel foreach where the N+1
instances of the enclosed scope activity will occur in parallel. In
essence an implicit flow is dynamically created with N+1 copies of the
foreach's enclosed scope activity as children. Each copy of the scope
activity will have the same counter variable defined in the same manner
as specified for serial foreach with the exception that each counter
variable will be uniquely initialized to one of the integer values
starting with startCounterValue and covering all integer values up to
and including finalCounterValue. In the case of parallel foreach the
count attribute acts as a validator of the startCounterValue and
finalCounterValue.

Add to Appendix A:

forEachCounterError - Either the startCounterValue or finalCounterValue
returned non-integer values or their relative values violated the
constraint specified by the count attribute.


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